Zaymiey

🧪 Chemistry  ·  Thermodynamics  ·  NEET & JEE

Hess's law states that the enthalpy change of a reaction:

Answer: Is independent of the path.

  • A Depends on the path taken
  • B Is independent of the path
  • C Is always exothermic
  • D Equals the activation energy

Correct answer: B. Is independent of the path

Explanation: Enthalpy is a state function, so ΔH depends only on initial and final states, not on the intermediate steps.

P-V Diagram: Isothermal vs Adiabatic ExpansionVPIsothermal (T constant)Adiabatic (q=0)Adiabatic curve is steeper: no heat enters to cushion the pressure drop

Isothermal expansion follows a gentler curve (heat flows in to keep T constant) while adiabatic expansion drops in pressure more steeply (no heat exchange, so internal energy and temperature fall as the gas does work).

Concept context

Study energy changes in chemical reactions. Understand enthalpy, entropy, Gibbs free energy, and the laws of thermodynamics that decide whether a reaction will occur spontaneously or not.

Read the full Thermodynamics notes →